In situ surface pH measurement during electrolysis using a rotating pH electrode

Abstract

An In situ technique has been developed for measuring the surface pH adjacent to a solid electrode/liquid Interface during electrolysis. Measurements of the surface pH can be used to obtain insights regarding the eiectrodeposltlon of various transition metals and to obtain a better understanding of associated in situ surface chemistry effects. Many transition metals and alloys deposit with simultaneous hydrogen evolution and, as a result, are accompanied by a pH rise near the cathode, thereby affecting the reactivity of the nearby metal-Ion species. Measurements of the surface pH of a solution containing simple salts during hydrogen evolution from a cathode were performed. The surface pl-l of a cathode during Ni and NiFe eiectrodeposltlon was also measured. The experiments demonstrated that, in the absence of buffers or metal ions, the surface pH rises many pH units above the bull( value. During Ni and NiFe eiectrodeposltlon, however, the surface pH of solutions consisting of simple salts and starting from a bulk pl-i level of 2 does not increase more than 3 pH units from the bulk value. In the case of NI and NiFe eiectrodeposltlon, surface buffering occurs because of the hydrolysis of the metal-ion species present. Additionally, it is found that during the anomalous codeposition of NiFe, the surface pH is much lower than that required by the Dahms-Croil hypothesis.^Copyright 1993 by International Business Macliines Corporation. Copying in printed form for private use is permitted without payment of royalty provided that (1) each reproduction is done without alteration and (2) the Journal reference and IBM copyright notice are included on the first page. The title and abstract, but no other portions, of this paper may be copied or distributed royalty free without further permission by computer-based and other information-service systems. Permission to republish any other portion of this paper must be obtained from the Editor.

Template-Assisted Electrodeposition of Fe-Ni-Co Nanowires: Effects of Electrolyte pH and Sodium Lauryl Sulfate

“…Both Fe and Ni ion reduction are expected to be under predominately kinetic control, but Co may be influenced by mass transport changes The change in current efficiency as the nanowire grows could also change the local pH and hence composition, as reported by Geng et al 17 for the same electrolyte presented here. Deligianni and Romankiw 43 have confirmed a surface pH rise during Ni-Fe thin film deposition. They noted that the pH would not be expected to increase more than 3 pH units from the bulk, with a buffering effect presented by the formation of hydrolysis of the metal-ion species.…”

Mesh-capped probe design for direct pH measurements at an actively corroding metal surface

“…In different arrangements, flow can be readily created by other means (e.g., by flush mounting the probe at a pipe wall or a flow channel wall, using a jet impingement setup, etc.). All these alternatives appear to be easier than rotating the metal mesh, as was done by Romankiw [22].…”

“…During the corrosion of the mesh, surface pH can be monitored. This surface pH probe design was further modified for rotating [22] or fixed [23,24] metal meshes. Particular applications were reported for surface pH measurement during jet impingement tests [24], electrodeposition [25,26] and electrochemical reduction reactions [27].…”

Cathodic inhibition and anomalous electrodeposition of Zn–Co alloys

“…With the initial electrolyte pH 5.0, they observed a rise in pH that might cause precipitation of Zn(OH) 2 while inhibiting Co deposition. But other researchers [11][12][13][14] (with the initial pH less than 4.0) could not find a significant pH increase that could result in Zn(OH) 2 .…”